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Title: Allelic variants in the PRR37 gene play and the human-mediated dispersal and diversification of sorghum

Author
item Klein, Robert - Bob
item MILLER, FREDERICK - Mmr Genetics, Llc
item Dugas, Diana
item BROWN, PATRICK - University Of Illinois
item BURRELL, A. MILLIE - Texas A&M University
item KLEIN, PATRICIA - Texas A&M University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2015
Publication Date: 5/16/2015
Citation: Klein, R.R., Miller, F.R., Dugas, D.V., Brown, P.J., Burrell, A., Klein, P.E. 2015. Allelic variants in the PRR37 gene play and the human-mediated dispersal and diversification of sorghum. Theoretical and Applied Genetics. DOI 10.1007/s00122-015-2523-z.

Interpretive Summary: This manuscript describes the domestication and dispersal of sorghum, a tropical cereal that is integrally associated with the historic movement of humans across Africa, Asia, and eventually to the Americas. This study focuses on a key adaptive gene and the selection of locally adaptive alleles by humans during the dispersal of sorghum to temperate climates worldwide. Placed in the context of historical records, we present a model of the origins of locally adapted day-neutral alleles that arose during the spread of sorghum cultivation to temperate ecosystems across the continents of Africa, Asia, and the Americas. Without the parallel selection of these day-neutral alleles, the spread of sorghum cultivation to long-day ecosystems would have been delayed or stalled. While primarily used as a grain crop, sorghum has also been historically selected by humans for use as a forage grass for animals, for stem sugar content to make syrup (molasses), and for broom construction in Asia; each of these specialized agronomic types displayed a different day-neutral allele that revealed their unique breeding history.

Technical Abstract: The domestication and spread of crops by early humans is of interest from a historical perspective and is of practical importance to present-day agriculturists. From its origin in northeastern Africa, cultivation of the tropical cereal sorghum spread north and south of the equator beginning approximately 3,500 years ago, and mutations in critical photoperiod-responsive genes occurred, permitting grain production in temperate ecosystems. Here, we show parallel selection by early humans in distant temperate ecosystems of an allelic series in a key adaptive gene by sequencing 4 kb of the photoperiod-responsive gene, ma1, in historic sorghum cultivars and landraces. Uniquely adaptive day-neutral ma1 alleles were also discovered in specialized agronomic cultivars including forage, sweet-stem, and broomcorn sorghums. Through this allele phylogenetic analysis of the ma1 gene, we obtained a more precise understanding of sorghum's global diversification and further insight into the selection history and gene flow of this key adaptive gene.